Current research is concerned with the study of the neurophysiological processes involved in normal coordinated movements of the mandible. Monkeys are used as subjects. Some animals are trained to produce controlled voluntary mandibular movements, and others are simply given pieces of natural food in order to obtain normal masticatory movements. Goals are to study the activity patterns of masticatory muscles, their physiological characteristics, and the activity patterns of neurons in the motor nucleus of the trigeminal nerve, brainstem interneurons in the region of the motor nucleus, and masticatory muscle afferents in relationship to such movements. Other experiments are directed to the study of single motor units of the jaw closing muscles, the role of oral sensory inputs in control of biting force, and the nature of direct auditory effects on jaw motoneurons. BIBLIOGRAPHIC REFERENCES: Goodwin, G.M. and Luschei, E.S. Discharge of spindle afferents from jaw closing muscles during chewing in alert monkey. J. Neurophysiol., 1975, 38:561-571. Luschei, E.S. and Goodwin, G.M. Role of monkey precentral cortex in control of voluntary jaw movements. J. Neurophysiol., 1975, 38:146-157.